Waterproof plastic



Reissued Feb. 5, 1929.

UNITED STATES ORLANDO A. COLLINGS, OF KANSAS CITY,

PATENT OFFICE.

MISSOURI, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO SILICA PRODUCTS (10., OF LOS ANGELES, CALIFORNIA, A CORPORATION OF DELAWARE.

WATERPROOF PLASTIC.

No Drawing. Original No. 1,650,864, dated November 29. 1927, Serial No. 549,211,'fi.cd April 3, 1922. Application for reissue filed October 20, 1928. Serial No. 313,938.

This invention relates to waterproof plastics and more particularly to waterproof,

plastic, hydraulic cements and mortars, and concrctes made from these; and it comprises a method of waterproofing concrete. stucco, mortar, plaster of Paris, ctc., wherein, the materials employed for making such a plastic are admixed, at the time of gaging the inert fillers, or prior thereto, with an insoluble dry mineral matter of the nature of a gelatinizable reversible colloid7, such as d y bentonite'; and it further comprises as a new and waterproof material, a set calcareous plastic material containing disseminated particles of a relatively dry mineral material having the properties of a gelatinizable reversible colloid, such as bentonite; all as more fully hereinafter set forth and as claimed.

For the present purposes, concrete may be regarded as a rigid skeleton of coarse aggregate (gravel, broken rock or the like) containing a finer aggregate (sand, etc. and cement) in its voids as a binder. As water and cement after settling do not have quite their original joint volume and as a limit is placed to the contraction of the concrete as a whole by the rigidity of the coarser aggregate, it follows that such a concrete must be, of necessity, more or less'minutely pervious. The degree of perviousness can be and is much reduced by proper selection and 'proportioning of materials and by correct methods of mixing and applying the concrete and with the correct proportion of water and with proper plasticity of the mixture; but there an irreducible minimum of perviousncss with the best of work. Sometimes this pervious character is unimportant, as in cases where the concrete is not used in wet or moist situations. But sometimes. the peryious character is a serious objection. as in concrete exposed to water under hydrostatic head, in stucco coatings. etc.

it isthe purpose of the present invention to obviate this penctral'iility lay water. To this end, I use in concrete 0t normal composition, in addition to the usual materials, a small proportion of a dry mineral matter having the properties of a reversible swelling or gelatinizable colloid to produce aplastic mass with water, capable of swellin with water and of being dried without forfeiting its swellir g power on again wetting. Many materials of this character are known, such as partially dehydrated silica and alumina gels and certain natural and artificial sili cates. But I regard some varieties of a mineral known as bcntonit-e as the most available for the present purposes. Bentonite on prolonged contact with large excess of water takes up large amounts thereof with a great increase in volume. Some varieties of minerals called bentonitc on drying lose this swellingpower but with others of the typical hentonite character the swollen mineral can be dried with contractioiLto its original volume and withoutforfeiting its power of swelling again when moistened, although some lose the swelling property in part only. Bentonite of this typical character is best adapted for my purpose. Although sometimes regarded as being, generically, a clay, bentonite is not really a clay in the ordinary sense. Unlike clays, a moderate degree of roasting does not impair materially its property of taking up water to form a plastic mass. Like the clays, however, the presence of free lime tends to hinder, though it does notovercome, its assuming a dispersoid state or condition; and, for this reason and because its hydration requires time. it can be admixed with the wet concrete batch without much moistening or complete swelling. The water of the wet mix goes preferentially to the cement constituents during the timc'occupied in setting and the hentonite particl s are intimately mixed with the water physically but withoutcomplete chemical combi nation, so that the bentonite subsequently remains in a condition in which it is able to take up water. After the concrete is set these minerals are hydrated and the bulk of the free lime has disappeared so that free swelling of the bentonite by water is no longer inhibited.

I find it rather better to give the hentonite a slightroast preliminary to using it for the present purposes. heating it to a. temperature at which it, is dried and perhaps somewhat dehydrated but not to any temperature at which it will lose the property of free swelling with water here important. The bentonite is advantageously used in a rather coarse condition although for some purposes, it may be used in a somewhat finer condition. It may be admixed with cement in the clinker grinding mills or added to the mix just prior to making the concrete. As is well known, clinker is the product referred to in the burn- 'lnixed with the water physically but withing of argillaceous and calcareous materials 2. The process of preparing a. calcareous in rotary or vertical kilns in the production plastic capable of becoming impervious to of natural and Portland cements. The purwater on accessiof moisture which comprises pose of mixing the bentonite with the clinker mixing dry bentonite with water and a ceis to obtain a more complete and intimate mentof the Portland cement type, the amount mixing. It is to be observed that the benof water used being merely that which will tonite may also be added to the ground cebe taken up by the cement.

ment at any stagev between the clinker mills 3. A set calcareous cement of normal comand the mortar. or concrete mixer. The position containing unswollen bentonite caamount of bentonite added is that which is pableof swelling on access of moisture. necessary for retaining the plastic properties 4. Concretecomposed of a. set concrete of and gii'ingwaterproof qualities, and will vary the Portland cement type and of normal comwithin widelimits, depending upon the exposition, said concrete containing unswollen tent of the plasticand waterproof properties bentonite capable of swelling on access of desired and the qualitiescof bentonite used. moisture.

In the concrete, it does not swellto any mate- 5. As a concrete, a set cement containing rial extent during mixing and setting, for in addition to the aggregate an unswollen reasons stated ante, nor is it much affected material of the nature of a gelatinizablereby the cement; it remains in the wet material versiblc colloid. i

in its orginal unhydrated state during" the (3. A set cement containing unswollen bensetting, the particles are. however, intimately tonite. i

7. k plastic composition which will set to out permanently taking on the water chelniform a waterproof concfete comprising Portcally. On subsequent exposure of the said land cement and approximately tive per cent concrete to water, the moisture entering of bentonite.

through any pore encounters the bentonite 8. The process of making awatcrproof and swells it. effectually plugging the pore. concrete which comprises the addition to a Concrete made with 2 to 5 per cent bentonite Portland cement mixture Of approximately is capable of withstanding considerable hyfive per cent of bentonite.

drostatic heads of water. Higher propor- 9. A waterproof Portland cement concrete tions may be used. of at least normal strength characterized by Dry bentonite may be admixed with plaster the admixture of approximately five per cent of Paris prior to making molded objects with of bentonite with the cement before it has set. the same results and the same advantages. 10. Set calcareous cement containing ben- It may be used in lime mortars and other caltonite in such condition as to swell upon access careous plastics but I regard its most adranof n'ioistu're thereto, thereby rendering said tageous use as in connection with concrete cement imper ious to water. I and stucco. A layer of concrete, water- 11. A ccmentitious composition consisting proofed in the present manner, may be advanof an intimate dry mitxure of ground cement tageously used as a facing for ordinary conclinker and a gelatinizable mineral matter. crete in walls intended to resist dampness or 12. A con'iposition, consisting of hydraulic water; building walls, reservoir walls, recement and hentonite adapted to form a plastaining walls, roofing tiles and facing, etc. tic upon the addition of water.

Bentonite may be mixed with cement and 11-}. A dryinortar capable of setting only water alone and used in relations where neat by the addition of water consisting of an inticement is employed. A mixture of bentonitc, mate inixtiu'e of Portland cement in which cement and sand is useful in making water is incorporated a quai'itity of beutonite and tight joints, as in roofing work or water tight an inert filler.

facings.

Unlike other waterproofing additions to concrete bentonite does not lessen the strength but increases it.

\Vhat I claim is 1 1. A potentially reactive dry plastic mix consisting of Portland cement, bentonitc, a d an inert filler.

15. potentially rcacliw dry plastic mix consisting of Portland cement, licntonite and 1. The process of preparing a calcareous an aggregate. i plastic capable ot becoming impervious to In testimony whereof. l have. hereunto water on access of moisture which comprises altixcd my signatm'e.

oimnino A. ooLmNos.

incorporating dry bentonite into such a plas tic. 1 

